  SEQ CHAPTER \h \r 1 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D. C.  20460

		

	OFFICE OF

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES



August 283, 2007

									PC Code: 	098301

									DP Barcode:	D299868

MEMORANDUM

SUBJECT: 	Use of Aldicarb for Lygus Bug Suppression, Aphids, and Mites
on Alfalfa Grown for Seed Production

FROM: 	Jonathan Angier, Ph.D., Environmental Scientist

		Jeannette Martinez, Biologist

Environmental Risk Branch 2

		Environmental Fate and Effects Division (7507C)	

		

TO:		Sherrie Kinard, PM

Robert McNally, Branch Chief

		Special Review and Reregistration Division (7508P)	 

THROUGH:	Dana Spatz, Branch Chief

Environmental Risk Branch 2

		Environmental Fate and Effects Division (7507C)	

This memorandum addresses the use of aldicarb on alfalfa grown for seed.
 This use is allowed only in the state of California, as a section 24(c)
Special Local Need Supplemental Label (EPA SLN No. CA-970011), 2005. 
Aldicarb is used on alfalfa grown for seed production to control Aphids,
Mites, and for Lygus Bug suppression.  Applications are 14 to 20 pounds
of product (Temik® 15G) per acre, or 13 to 18 ounces of product per
1,000 feet of row.  Aldicarb granules are drilled in and covered with an
undefined soil depth (“minimum depth of soil”).  Care must be taken
not to injure roots during application, indicating that soil
incorporation may be problematic.

Alfalfa is a minor use for aldicarb, so there is little or no specific
monitoring data targeted to this use.  Instead, aquatic exposure for
aldicarb use on alfalfa was estimated using EFED’s Tier 2 PRZM-EXAMS
model.  The PRZM scenario is the same as used in the Aldicarb California
Red-Legged Frog Endangered Species Assessment (2007) for alfalfa.

Physical and chemical model input parameters are listed in Table 1.  An
incorporation efficiency of 85% was used.  The CAM 8 setting was
utilized assigning all the ‘unincorporated’ granules (15%) to a
depth of 0.1 cm (1 mm) below the surface, with the remaining 85% assumed
to be unavailable for runoff.  Maximum application rates and minimum
intervals (where applicable) were used.

Table 1.  Aldicarb Inputs Used in PRZM-EXAMS Runs for Alfalfa

Input Parameter	Value	Reference/Comment

Molecular Weight 	190.2 g/mol	MRID 00152095

Henry’s Law Constant	1.7 E-10 atm-m^3/mol	Acc 255979

Vapor Pressure	2.6 E-5 @ 25°C	MRID 00152095

Solubility	6,000 mg/L	Acc 255979

Kd	0.12	Minimum non-sand value for aldicarb sulfone (MRID 43560302)

Hydrolysis	pH 5, stable (0)

pH 7, stable (0)

pH 9, 60 days	Parent hydrolyzed only at pH 9 (MRID 00102065) –
degradates may hydrolyze more rapidly at neutral-to-high pH

Aqueous Photolysis Half-life	4 days	MRID 42498201

Water Half-life	12 days 	MRID 44592107. Single acceptable guideline
study for parent / sulfoxide / sulfone (4days) x 3; corresponds w/ DT90

Benthic Half-life	24 days	No data; use 2X aerobic aquatic half-life

Soil Half-life	55 days	Upper 90th pct bound on mean for combined
parent+sulfoxide+sulfone half-life from 19 soils

Application Rate, Alfalfa	0.5 kg a.i./ha	20 lb product/A, a.i.= 15%, 15%
incorp.

FILTRA, UPTKF, PLVKRT, PLDKRT	0	Default values

FEXTRC	0.0	Soil incorporated

Additional Notes	Modeled total aldicarb residues	Half-life input values
based on combined aldicarb residues; lowest Kd of the 3 chemicals used
for mobility. Assumes equal toxicity of parent, degradates



Results indicate a ‘peak’ aquatic EEC of 10 ppb in surface water
under fairly high-risk conditions (see below).  This places alfalfa
consistent with many other aldicarb uses, in terms of estimated aquatic
exposure.  Given the nature of the required application methods
(drilling into side of plant rows), it is unlikely that greater
incorporation efficiency could be achieved without damaging roots. 
However, as a relatively minor use, alfalfa for seed production is not
likely to have a major, widespread impact on aquatic environments,
although there could be local effects from surface water exposure in
vulnerable high use areas.  

PRZM-EXAMS Model Results for Aldicarb Use on Alfalfa

Alfalfa (for seed) Aquatic EECs (ppb):

Peak		96 hr		21 Day	60 Day	90 Day	Yearly

10.05		9.55		8.41		5.27		3.76		0.942	

Average of yearly averages:	0.2962

Terrestrial exposure to birds and mammals was modeled using the OPP/EFED
Tier 1 T-REX model, version 1.2.3.  The 24(c) label recommends a 30 inch
spacing (SLN # CA-970011), while the University of California cites
alfalfa management practices applying six to seven inch spacing between
alfalfa seed rows (  HYPERLINK
"http://ucce.ucdavis.edu/files/filelibrary/2129/18336.pdf" 
http://ucce.ucdavis.edu/files/filelibrary/2129/18336.pdf ). The Agency
will estimate risk to terrestrial wildlife by calculating two sets of
avian and mammalian RQs where the row spacing parameter alone will be
varied between runs. The estimated RQs derived from aquatic and
terrestrial EECs are presented in Table 2 and 3, respectively.

Use of granular aldicarb on alfalfa for seed with a one time application
rate of 20 lbs of product/acre is expected to result in exceeded Levels
of Concern (LOC) for freshwater and estuarine/marine fish as well as
freshwater and estuarine/marine invertebrates. More specifically, there
are acute and chronic LOC exceedances for freshwater and
estuarine/marine non-target invertebrates, acute restricted use, acute
endangered species, and chronic LOC exceedances for freshwater and
estuarine/marine fish.  RQs range from 0.19 to 14.64 (see Table 2).

Table 2.  Acute and Chronic Risk Quotients for Freshwater (Alfalfa for
Seed Scenario)

Effects to Species	Aquatic Species	Toxicity Value

(ppb)	EEC 

(ppb)	RQ	LOC Exceedance

Acute	Bluegill sunfish	96-hr LC50 = 52	10.05 (peak)	0.19	Yes2,3

Chronic	Bluegill sunfish	NOAEC = 0.46	5.27 (60-d)	11.46	Yes1,2,3

Acute	Sheepshead minnow	96-hr LC50 = 41		10.05 (peak)	0.25	Yes2,3

Chronic	Sheepshead minnow	Estimated NOAEC = 0.36	5.27 (60-d)	14.64
Yes1,2,3

Acute	Chironomus tetans	48-hr EC50 = 20	10.05 (peak)	0.50	Yes1,2,3

Acute	Pink shrimp	96-hr LC50 = 12 ppb	10.05 (peak)	0.84	Yes,,

Chronic	Mysid shrimp (est/marine, freshwater inverts)	NOAEC = 1
8.41(21-d)	8.41	Yes



Similarly, use of aldicarb on alfalfa for seed with a one time
application rate of 20 lbs of product (15G)/acre is expected to result
in exceeded Levels of ConcernLOCs for birds and mammals of all sizes.
Small birds and mammals are at greatest acute risk from exposure to
aldicarb; RQs (six inch and 30 inch row spacing, respectively) for small
birds are s are 451.23 and 2256.17 and for small mammals are157.93 and
789.64, respectively. RQs (six inch and 30 inch row spacing,
respectively) for large birds are 5.02 and 25.09 and for large mammals
are 5.02 and 6.77, respectively and 33.85 (see Table 3 and 4, Appendix
B). . Taxa specific RQ values differ by a magnitude of five between both
modeling runs. The 30 inch row spacing, as recommended by the 24(c)
label, leads to the highest RQ values and greater risk to terrestrial
wildlife. The six inch row spacing, as suggested by the University of
California Intermountain Alfalfa Management document, still leads to
greatly exceeded LOCs for terrestrial wildlife although RQ values are
smaller 

The Agency is currently unable to quantitatively assess chronic risk for
birds due to a lack of data. However, based on inference from mammalian
data, which involved comparing magnitudes of LD50’s between the
mallard duck (1.0 mg/kg-bw) and rat (0.9 mg/kg-bw) and then using this
information together with the chronic information available for the
laboratory rat (reproductive NOAEL = 0.7 – 0.9 mg/kg-bw; MRID
42148401), the Agency expects that birds (as well as mammals) that
survive acute exposure from aldicarb may suffer adverse reproductive
(chronic) effects.

Table 3.  Acute Risk Quotients for Terrestrial Wildlife (Alfalfa for
Seed Scenario)

Effects to Species	Terrestrial Species	Toxicity Value

	LD50/sq.ft.	LOC Exceedance

Acute	Mallard duck	LD50 = 1.0 mg/kg-bw



	Small bird  – 20 g	451.23	Yes1,2,3

	Medium bird – 100 g	70.89	Yes1,2,3

	Large bird – 1000 g	5.02	Yes1,2,3

Acute	Laboratory rat	LD50 = 0.9 mg/kg-bw



	Small mammal – 15 g	157.93	Yes1,2,3

	Medium mammal – 35 g	83.65	Yes1,2,3

	Large mammal – 1000 g	6.77	Yes1,2,3



Table 4. Acute Risk Quotients for Terrestrial Wildlife (Alfalfa for Seed
Scenario)

Effects to Species	Terrestrial Species	Toxicity Value

	LD50/sq.ft.	LOC Exceedance

Acute	Mallard duck	LD50 = 1.0 mg/kg-bw



	Small bird  – 20 g	2256.17	Yes1,2,3

	Medium bird – 100 g	354.45	Yes1,2,3

	Large bird – 1000 g	25.09	Yes1,2,3

Acute	Laboratory rat	LD50 = 0.9 mg/kg-bw



	Small mammal – 15 g	789.64	Yes1,2,3

	Medium mammal – 35 g	418.26	Yes1,2,3

	Large mammal – 1000 g	33.85	Yes1,2,3



As mentioned above, aldicarb use on alfalfa for seed production is
limited in scope (restricted to the state of California), so widespread
exposures and resultant deleterious effects (in both terrestrial and
aquatic environments) will likely be limited to use areas and nearby
vicinities.  However, considering that there are LOC exceedences for
every category in both aquatic and terrestrial environments, there is a
high likelihood of risk to aquatic and terrestrial organisms in areas
where aldicarb is used on alfalfa; this is especially true in the
terrestrial sector, where LOCs are greatly exceeded (see Table 3 and
4).APPENDIX A:	PRZM-EXAMS Runs for Alfalfa

stored as CAalf.out

Chemical: Aldicarb

PRZM environment: CAalfalfa_NirrigOP.txt	modified Tueday, 8 June 2004 at
08:02:02

EXAMS environment: pond298.exv	modified Thuday, 29 August 2002 at
16:33:30

Metfile: w93193.dvf	modified Wedday, 3 July 2002 at 09:04:24

Water segment concentrations (ppb)

Year	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

1961	1.155	1.081	0.8247	0.4691	0.3242	0.08409

1962	0.0422	0.03937	0.0299	0.01918	0.01439	0.006742

1963	10.05	9.431	8.431	5.235	3.725	0.932

1964	0.04612	0.04343	0.0341	0.02067	0.01478	0.004053

1965	4.998	4.716	3.677	2.184	1.555	0.3895

1966	0.03861	0.0366	0.03136	0.02296	0.0153	0.003785

1967	10.03	9.565	8.253	5.282	3.773	0.9437

1968	6.976	6.531	5.018	2.932	2.066	0.526

1969	7.673	7.223	5.665	3.282	2.314	0.5819

1970	0.1925	0.1836	0.1652	0.08991	0.05994	0.01518

1971	9.226	8.698	6.825	4.032	2.834	0.7172

1972	0.6155	0.5461	0.3465	0.1598	0.1082	0.02754

1973	0.4687	0.4381	0.3347	0.2119	0.1623	0.04044

1974	0.5205	0.4897	0.3831	0.2265	0.1594	0.05611

1975	0.05145	0.04851	0.04078	0.02926	0.02004	0.008912

1976	0.01549	0.01497	0.01302	0.01002	0.008083	0.003147

1977	0.2769	0.2579	0.1942	0.09803	0.0666	0.01673

1978	20.93	19.72	16.23	9.758	6.879	1.712

1979	0.02495	0.02378	0.01966	0.01201	0.008005	0.001989

1980	0.01043	0.01001	0.008502	0.005942	0.004616	0.001652

1981	2.739	2.556	1.932	1.033	0.7055	0.1768

1982	13.12	12.45	10.02	6.073	4.311	1.078

1983	0.4093	0.3797	0.268	0.1609	0.1132	0.02823

1984	0.01921	0.01796	0.01434	0.009731	0.007559	0.001861

1985	0.04949	0.04598	0.03574	0.02878	0.02534	0.009365

1986	0.01601	0.01542	0.01156	0.007419	0.005634	0.002293

1987	5.611	5.095	3.491	1.676	1.143	0.2847

1988	10	9.382	7.889	4.602	3.219	0.7962

1989	2.999	2.745	1.941	0.98	0.6673	0.1676

1990	4.148	3.843	2.803	1.561	1.082	0.2684

Sorted results

Prob.	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

0.032258064516129	20.93	19.72	16.23	9.758	6.879	1.712

0.0645161290322581	13.12	12.45	10.02	6.073	4.311	1.078

0.0967741935483871	10.05	9.565	8.431	5.282	3.773	0.9437

0.129032258064516	10.03	9.431	8.253	5.235	3.725	0.932

0.161290322580645	10	9.382	7.889	4.602	3.219	0.7962

0.193548387096774	9.226	8.698	6.825	4.032	2.834	0.7172

0.225806451612903	7.673	7.223	5.665	3.282	2.314	0.5819

0.258064516129032	6.976	6.531	5.018	2.932	2.066	0.526

0.290322580645161	5.611	5.095	3.677	2.184	1.555	0.3895

0.32258064516129	4.998	4.716	3.491	1.676	1.143	0.2847

0.354838709677419	4.148	3.843	2.803	1.561	1.082	0.2684

0.387096774193548	2.999	2.745	1.941	1.033	0.7055	0.1768

0.419354838709677	2.739	2.556	1.932	0.98	0.6673	0.1676

0.451612903225806	1.155	1.081	0.8247	0.4691	0.3242	0.08409

0.483870967741936	0.6155	0.5461	0.3831	0.2265	0.1623	0.05611

0.516129032258065	0.5205	0.4897	0.3465	0.2119	0.1594	0.04044

0.548387096774194	0.4687	0.4381	0.3347	0.1609	0.1132	0.02823

0.580645161290323	0.4093	0.3797	0.268	0.1598	0.1082	0.02754

0.612903225806452	0.2769	0.2579	0.1942	0.09803	0.0666	0.01673

0.645161290322581	0.1925	0.1836	0.1652	0.08991	0.05994	0.01518

0.67741935483871	0.05145	0.04851	0.04078	0.02926	0.02534	0.009365

0.709677419354839	0.04949	0.04598	0.03574	0.02878	0.02004	0.008912

0.741935483870968	0.04612	0.04343	0.0341	0.02296	0.0153	0.006742

0.774193548387097	0.0422	0.03937	0.03136	0.02067	0.01478	0.004053

0.806451612903226	0.03861	0.0366	0.0299	0.01918	0.01439	0.003785

0.838709677419355	0.02495	0.02378	0.01966	0.01201	0.008083	0.003147

0.870967741935484	0.01921	0.01796	0.01434	0.01002	0.008005	0.002293

0.903225806451613	0.01601	0.01542	0.01302	0.009731	0.007559	0.001989

0.935483870967742	0.01549	0.01497	0.01156	0.007419	0.005634	0.001861

0.967741935483871	0.01043	0.01001	0.008502	0.005942	0.004616	0.001652

0.1	10.048	9.5516	8.4132	5.2773	3.7682	0.94253

					Average of yearly averages:	0.296203966666667

Inputs generated by pe4.pl - 8-August-2003

Data used for this run:

Output File: CAalf

Metfile:	w93193.dvf

PRZM scenario:	CAalfalfa_NirrigOP.txt

EXAMS environment file:	pond298.exv

Chemical Name:	Aldicarb

Description	Variable Name	Value	Units	Comments

Molecular weight	mwt	190.2	g/mol

Henry's Law Const.	henry	1.7E-10	atm-m^3/mol

Vapor Pressure	vapr	2.55E-5	torr

Solubility	sol	6000	mg/L

Kd	Kd	0.12	mg/L

Koc	Koc		mg/L

Photolysis half-life	kdp	4	days	Half-life

Aerobic Aquatic Metabolism	kbacw	12	days	Halfife

Anaerobic Aquatic Metabolism	kbacs	24	days	Halfife

Aerobic Soil Metabolism	asm	55	days	Halfife

Hydrolysis:	pH 5	0	days	Half-life

Hydrolysis:	pH 7	0	days	Half-life

Hydrolysis:	pH 9	60	days	Half-life

Method:	CAM	8	integer	See PRZM manual

Incorporation Depth:	DEPI	0.1	cm

Application Rate:	TAPP	0.504	kg/ha

Application Efficiency:	APPEFF	1	fraction

Spray Drift	DRFT	0	fraction of application rate applied to pond

Application Date	Date	31-3	dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17:	FILTRA	

	IPSCND	1

	UPTKF	

Record 18:	PLVKRT	

	PLDKRT	

	FEXTRC	0.0

Flag for Index Res. Run	IR	Pond

Flag for runoff calc.	RUNOFF	none	none, monthly or total(average of
entire run)

APPENDIX B:	T-REX Modeling for Alfalfa

Input Parameters Run 1:

Input Parameters Run 2:

Modeling Output Run 1:

Modeling Output Run 2:

 acute LOC for non-target organism ≥0.5 (aquatic animals, mammals,
birds)

Acute restricted use LOC ≥0.2 (mammals, birds), ≥0.1 (aquatic
animals)

 Acute endangered species LOC ≥0.1 (mammals, birds), ≥0.05 (aquatic
animals)

 Chronic RQ ≥1 (aquatic animals, mammals, birds)

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OPP/BEAD (2007), University of California (1997),
http://ucce.ucdavis.edu/files/filelibrary/2129/18336.pdf); Bandwidth =
6.00 inches

 Incorporation = 85%; Application type = banded; Row spacing = 30 inches
(US EPA, SLN# CA-970011); Bandwidth = 6 inches

